I re-made a stage in my case, which is crashed a moment ago. Yesterday, it was totally fine but when I open it again today, it is failed (ActivityStatusError window suddenly popped up) and I can't open the stage anymore. Please help, I need a guidance to fix it. I am using Pega 7.1.9 and I added the screenshot below.
is your Case present in Data-Class? Collect the tracer while opening stage and check for error. Primary Page when error has occurred is referring to data class I believe, but harness is not Data-class or not in its inheritance hierarchy. Mostly you will understand the issue by checking tracer.
Please submit an SR with Tracer, PegaRules.log and CaseType.xml if you need GCS help further on this.